[shuffle] Move program_id to new structure.

This CL moves the `program_id` to `utils/generation_id`. The program id
was renamed as it's also used by symbol which lives at a different
layering to the AST program.

Bug: tint:1988
Change-Id: I50146ac25e89e269276f9f7030ada989c98db66e
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/142861
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Dan Sinclair <dsinclair@chromium.org>
diff --git a/src/tint/utils/text/symbol.cc b/src/tint/utils/text/symbol.cc
index 731f66e..7b51f7f 100644
--- a/src/tint/utils/text/symbol.cc
+++ b/src/tint/utils/text/symbol.cc
@@ -20,8 +20,8 @@
 
 Symbol::Symbol() = default;
 
-Symbol::Symbol(uint32_t val, tint::ProgramID pid, std::string_view name)
-    : val_(val), program_id_(pid), name_(name) {}
+Symbol::Symbol(uint32_t val, tint::GenerationID pid, std::string_view name)
+    : val_(val), generation_id_(pid), name_(name) {}
 
 Symbol::Symbol(const Symbol& o) = default;
 
@@ -34,17 +34,17 @@
 Symbol& Symbol::operator=(Symbol&& o) = default;
 
 bool Symbol::operator==(const Symbol& other) const {
-    TINT_ASSERT_PROGRAM_IDS_EQUAL_IF_VALID(Symbol, program_id_, other.program_id_);
+    TINT_ASSERT_GENERATION_IDS_EQUAL_IF_VALID(Symbol, generation_id_, other.generation_id_);
     return val_ == other.val_;
 }
 
 bool Symbol::operator!=(const Symbol& other) const {
-    TINT_ASSERT_PROGRAM_IDS_EQUAL_IF_VALID(Symbol, program_id_, other.program_id_);
+    TINT_ASSERT_GENERATION_IDS_EQUAL_IF_VALID(Symbol, generation_id_, other.generation_id_);
     return val_ != other.val_;
 }
 
 bool Symbol::operator<(const Symbol& other) const {
-    TINT_ASSERT_PROGRAM_IDS_EQUAL_IF_VALID(Symbol, program_id_, other.program_id_);
+    TINT_ASSERT_GENERATION_IDS_EQUAL_IF_VALID(Symbol, generation_id_, other.generation_id_);
     return val_ < other.val_;
 }